Overlapping action

Overlapping action is something I talked about in my last post, but I think it's  worth going over again in a little more detail.Put simply, it's what happens when a part of a body(or an object) is delayed in relation to another part of the body (or object). I used the tail in the bouncy ball example to show overlap, but here's another one that illustrates it a little clearer:

I've drawn a fist hitting a hard surface. There's a drawing for when the arm is resting, one where it rises into the air (in anticipation) and then another where it comes down, hitting the surface.

Because, like I mentioned before, it's best not to concentrate on too many things at once, I'm only going to work on the upper arm for now. When the arm comes down I want it to be really fast, so I'll use less frames.

Less frames create the illusion of speed and more frames does the opposite. I'll uses more frames as the arm reaches it's highest point, and less as it starts to come down. That way it'll look like the hand slams down on the hard surface.

Here's the result. Now I need to figure out the animation for the lower arm. When the upper arm moves I want the lower arm to drag a few frames behind and then catch up when the upper arm stops moving. The same goes for when it slams back down.. I'll use a simple line to make the process a little easier for myself drawing-wise.

Okay, so now I have the lower arm roughed in. Notice how when the upper arm stops moving the lower arm catches up to it a little later.

 Now I'll use that line as the basis for drawing the actual arm. 

I've drawn in the lower arm, so now all that's left is the hand, which I also want to delay. First I'll draw a line to represent where it'll be and then I'll draw a box once I've got the motion right. If the lower arm is a little delayed from the upper arm, then the hand should be a little delayed from the lower arm. When all of these parts overlap, it should create something similar to the Wave Principle I talked about in my last post.

Alright, now I've got most of the arm and hand done and have added fingers. I even animated a little bounce when the hand hits the hard surface. 

So that's overlapping action. It can be very helpful in making animation look fluid and more believable.